This invention relates to a process for preparing hydrocarbon blown, rigid polyurethane foam using a novel compatibilizing agent.
Many of today""s rigid foam formulations have been optimized for desirable processing and property characteristics using such common blowing agents as F-11 and HCFC-141b. Due to environmental concerns and associated legislative pressures, these and similar materials are being phased out over varying timetables in different countries. These market changes have created a need for alternative blowing agents for rigid foam applications. One of these potential alternatives involves the use of hydrocarbon blowing agents, such as isomers of pentanes and butanes, in place of the widely used and historical chlorofluorocarbons (CFC""s), hydrochlorofluorocarbons (HCFC""s), and hydrofluorocarbons (HFC""s). Unfortunately, these low polarity hydrocarbon blowing agents frequently possess limited compatibility with standard foam formulations optimized for the halogenated additives. Accordingly in the near term, the industry urgently needs additives that will improve the compatibility of these new blowing agents with the time-proven processing equipment and formulation chemistries. In time, evolving chemistries and/or manufacturing processes may obviate this compatibilizer need, but the industry needs tractable solutions today to meet current environmental and market demands.
Much art exists in the rigid polyurethane foam field detailing additives that render hydrocarbons more compatible with standard rigid foam formulation mixtures. This specific invention addresses additional novel additives and mixtures of additives that render hydrocarbon blowing agents more compatible with rigid foam formulations, possibly resulting in density reduction and more efficient use of the blowing agent.
WO 96/12759 (Dow) discloses a close-celled polyurethane foam comprising reacting in the presence of a hydrocarbon blowing agent, a polyisocyanate with a mixed polyol composition. This polyol mixture comprises a standard rigid polyol plus a compatibilizing agent containing the CnH2n+1 fragment, where n is greater than or equal to 5, which contains at least one active hydrogen and not more than one aromatic group. Castor oil is illustrated. The compatibilizing agents may be alkoxylated derivatives of fatty oils. No criticality for alkoxylation is noted and, more particularly no criticality of ethoxylation is suggested. U.S. Pat. No. 5,451,615 (Dow), a related patent, details compatibilizing agents which are fatty oils with hydroxyl values of 100-200.
U.S. Pat. No. 5,484,817 and U.S. Pat. No. 5,464,562 describe a method for preparing close- celled rigid polyisocyanate foam comprising reacting polyisocyanate and polyol having ester linkages with a C4-C7 hydrocarbon and a polyol additive. This additive is noted as a polyalkylene polyether monol (i.e. a mono hydroxy compound) based on a C8-C24 fatty hydrocarbon with one active hydrogen atom.
U.S. Pat. No. 5,470,501 and U.S. Pat. No. 5,504,125 describe polyurethane foam formulations using a hydrocarbon C4-C7 blowing agent and a compatibilizer. The noted compatibilizer is an optionally alkoxylated alkyl aromatic monol or derivative.
WO 98/42764 (ICI) discusses use of a mixture of two different polyoxyethylene polyether monols to solubilize hydrocarbon blowing agents in rigid polyurethane foams. C12-C15 monols with 120-180 hydroxyl values are discussed as solubilizing agents.
Skowronski and Londrigan, (Jim Walter Research Corp.) SPI 29th Polyurethane Conference, 1985 page 76-83 describes foams based on surfactants prepared from castor oil ethoxylates unto which were grafted maleate and fumarate esters via free radical coupling chemistries. These surfactants were reportedly used in phenolic closed celled foams as well as polyurethane foams and were substitutes for traditional silicone surfactants. A related patent, U.S. Pat. No. 4,529,745 describes surfactants which are free radical reaction products of polyoxyalkylene adducts of organic triglycerides with dibasic esters that possess unsaturated C4-C5 diacid cores and C8-C18 alcohol derived tails. Ethoxylated castor oil and tridecyl fumarate are preferred building blocks of these grafted surfactants.
U.S. Pat. No. 5,684,092 describes polyurethane foams employing hydrocarbon blowing agents and a 1-4 carbon monol other than t-butanol.
U.S. Pat. No. 5,786,400 (Sumitomo Bayer Urethane Co., Ltd.: Japan) describes the use of t-butanol as a hydrocarbon emulsifier in rigid foams. Data in Table 3 of the citation shows it to be more efficient compatibilizer than a nonylphenol ethoxylate additive or no additive.
U.S. Pat. No. 4,751,251 (Dow Corning) describes a blend of silicone, organic surfactant and water or C1 to C3 alcohols as a generic compatibilizer package. The document claims no negative effect is produced on foam reaction catalysis, even with acid functional organic surfactant, and observes increased foam height when using these mixtures. The preferred organic surfactant is reported to be sodium dodecylbenzene sulfonate.
U.S. Pat. No. 5,736,588 (Bayer Aktiengesellschaft) uses solution promoters of a group consisting of dialkyl carbonates, certain dicarboxylic acid esters, certain triesters of phosphoric acid, certain fatty acid/diamine reaction products, and certain quartemary ammonium salts. U.S. Pat. No. 5,578,651 describes similar solubilizers used in polyurethane foams employing halohydrocarbon blowing agents.
This invention relates to rigid foam mixtures comprised of polyol(s), isocyanate(s), blowing agent(s), catalyst(s), optional additive(s), and specific compatibilizing additives. The invention further relates to a novel process for preparing hydrocarbon blown rigid polyurethane foam using a compatibilizing agent.
The compatibilizing agent utilized in the invention is (1) an alkoxylate adduct of a triglyceride with a hydroxyl value of less than about 100. The triglyceride adduct (1) has an ethylene oxide content of at least 40% by weight of the adduct. These adducts may be used alone or in mixtures with other compatibilizers. The compatibilizers increase the stability of rigid foam formulation emulsions containing hydrocarbon blowing agents while showing little or no adverse affect to physical properties of foams prepared therewith.
The alkoxylated triglyceride additive (1) may optionally be employed with one or more adducts (2) from the following: a polyoxyalkylene oxide monol, a capped polyoxyalkylene oxide adduct, and a fatty oil, including triglyceride(s) or alkoxylated triglyceride(s), other than those defined for triglyceride adduct (1).
Another aspect of the present invention is the polyurethane foam/article made by curing a composition of the invention.
The entire disclosures of all US patents and other published documents and any copending US patent applications mentioned anywhere herein are expressly incorporated herein by reference
This invention relates to rigid foam mixtures comprised of polyol(s), isocyanate(s), blowing agent(s), catalyst(s), optional additive(s), and the compatibilizing additive of the invention. The compatibilizing agent(s) of this invention greatly enhance the stability of rigid foam formulation emulsions, particularly when prepared with higher hydrocarbon blowing agent levels. Compatibility improvements of 15% or more, as measured by an ability to relatively increase hydrocarbon levels without breaking the emulsion, can generally be obtained with the invention, often greater than 50%. In preferred embodiments of the invention the foam system can tolerate increased hydrocarbon levels which are 75% more higher than levels obtainable with conventional compatibilizers.
Rigid foam as discussed in this invention is one defined by its application. It is typically a fine, closed-cell foam material with ample bulk physical integrity and self-supporting character such as to be used as laminated building panels structural components in appliances, etc. This foam also often must possess high thermal resistance and high insulation properties with only a relatively slow increase in thermal conductivity over time. It may also be required to be low in friability, high in compressive strengths, and have low flammability.
The polyols used in the foam mixtures are compounds having two or more hydroxyl groups. They generally have a molecular weight between 50 and 12,000, more narrowly from about 200 to about 1,000. They may be polyether polyols, polyester polyols or other polyol compounds. Mixtures of polyols of various structures, molecular weights and/or functionalities may also be used.
The polyols which can be employed in the preparation of these foam compositions include, for example, monomeric polyols such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,4-butanediol, hexanetriol, glycerol, trimethylolpropane, triethylolpropane, pentaerythritol, sorbitol, mannitol, sucrose, and bisphenol A; polyethers such as polyethylene ether glycols, polypropylene ether glycols, polytetramethylene ether glycols, and alkylene oxide adducts of polyhydric alcohols, including those monomeric polyols listed above and wherein the oxyalkylene portion is derived from a monomeric unit such as ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, or mixtures thereof; hydroxyl terminated amines and alkoxylated adducts thereof; and alkylene oxide adducts of acids of phosphorous such as the adducts prepared by the reaction of phosphoric acid and ethylene oxide, phosphoric acid and propylene oxide, phosphorus acid and propylene oxide, phosphonic acid and ethylene oxide, phosphonic acid and propylene oxide, polyphosphoric acid and propylene oxide and phosphonic acid and styrene oxide.
Typical polyether polyols include polyoxyethylene glycol, polyoxypropylene glycol, polyoxybutylene glycol, polytetramethylene glycol, block copolymers, for example, combinations of polyoxyethylene glycol and polyoxypropylene glycol, poly-1,2-oxybutylene and oxyethylene glycols, and poly-1,4-oxybutylene and oxyethylene glycols, and random copolymer glycols prepared from blends or sequential addition of two or more alkylene oxides. Also adducts of the above with trimethylolpropane, glycerol, and hexanetriol as well as the polyoxypropylene adducts of higher polyols such as pentaerythritol, and sugar derivatives such as mannitol, sucrose sorbitol, and the like, may be employed. Alkoxylated bisphenols or polyphenols can also be used.
The polyol ether polymers which can be employed in the present invention include oxyalkylene polymers which have an oxygen/carbon ratio from about 1:2 to 1:4 and preferably an oxygen/carbon atom ratio from about 1:2.8 to 1:4 and from 2 to 6 terminal hydroxyl groups, preferably an average of about 2-4 terminal hydroxyl groups. The polyether polyols generally have an average equivalent weight from about 60-10,000 and preferably have an average equivalent weight from about 70-6,000, more preferably about 1,000 or less. Polyoxypropylene polyols having molecular weights from about 200 to 4000 corresponding to equivalent weights from about 70 to 400 and mixtures thereof are particularly useful as polyol reactants. Polyol blends such as mixtures of high molecular weight polyether polyols with lower molecular weight polyether polyols or monomeric polyols can also be employed.
Any suitable hydroxyl terminated polyester may also be used. These can be obtained from the reaction of polycarboxylic acids and/or esters and polyhydric alcohols. Such suitable polycarboxylic acids may include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, basillic acid, thapsic acid, maleic acid, fumaric acid, glutaconic acid, ortho-phthalic acid, isophthalic acid, and terephthalic acid. Suitable polyhydric alcohols include the following: ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol, 1,6-hexanediol, 1,5-hexanediol, glycerol, trimethylolpropane, trimethylolethane, hexane-1,2,6-triol, xcex1-methylglucoside, pentaerythritol, sorbitol, sucrose, and compounds derived from phenols such as 2,2-bis(4-hydroxyphenol) propane. Polyesters based on mixed acids and/or polyols may also be used. Polyester functionality typically spans from about 1.5 to 8 more preferably from about 1.8 to 4. Hydroxyl numbers typically range from about 100-600 (including residual diols) and more preferably from about 150-350 for these polyols. Mixtures of polyether and polyester polyols may also be employed within this invention.
In addition to the above hydroxyl-containing compounds, other compounds, which may be employed, include graft polyols. These polyols are prepared by the in situ polymerization product of a vinyl monomer in a reactive polyol medium and in the presence of a free radical initiator. The reaction is generally carried out at a temperature ranging from about 40xc2x0 C. to 150xc2x0 C.
Any organic isocyanates can be employed in the preparation of foams of the present invention. The organic polyisocyanates, which can be used, include aromatic, aliphatic, and cycloaliphatic polyisocyanates and combinations thereof. Representative of these types are the diisocyanates such as m-phenylene diisocyanate, toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, mixtures of the 2,4- and 2,6-toluene diisocyanates, hexamethylene-1,6-diisocyanate, tetramethylene-1,4-diisocyanate, cyclohexane-1,4-diisocyanate, hexahydrotoluene 2,4- and 2,6-diisocyanates, naphthalene-1,5-diisocyanate, diphenyl methane-4,4xe2x80x2-diisocyanate, 4,4xe2x80x2-diphenylene diisocyanate, polymethylenepolyphenyl isocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4xe2x80x2-diisocyanate, and various liquid diphenylmethane-diisocyanates containing a mixture of 2,4- and 4,4xe2x80x2 isomers. Especially useful are polymethylenepolyphenyl isocyanates. These isocyanates are prepared by conventional methods known in the art such as phosgenation of the corresponding organic amines. Crude polyisocyanates may also be used in the practice of this invention, such as crude toluene diisocyanate obtained by the phosgenation of a mixture of toluene diamines or the crude diphenylmethane diisocyanate obtained from the phosgenation of a mixture of crude methylene diphenylamines. Mixtures of any of these may be employed.
The amount of polyisocyanate present when preparing the polyurethane foams is such to provide for an isocyanate index of typically from about 60 to 350, preferably from around 80 to about 200. An isocyanate index of 100 corresponds to one isocyanate group per isocyanate reactive hydrogen atom present including those from the polyol composition, compatibilizing agent, and, if present, any water.
The polyurethane foaming process of this invention requires the presence of a hydrocarbon blowing agent that advantageously comprise a C4-C8 aliphatic or cycloaliphatic hydrocarbon being an alkane, alkene, or alkyne. Such hydrocarbons are selected as blowing agents because they have a boiling point lower than the reaction exotherm, generally more than about 120xc2x0 C., and usually from about 150xc2x0 C. to about 200xc2x0 C., encountered when preparing polyurethane foam. Suitable hydrocarbons include those having boiling points of less than 120xc2x0 C., and preferably less than 100xc2x0 C., and more preferably less than about 50xc2x0 C. Examples include i-butane, n-butane, n-pentane, i-pentane, cyclopentane, methylcyclopentane, hexane, cyclohexane, methylcyclohexane, isomers thereof, or mixtures of two or more thereof. Typically the hydrocarbon will be present in an amount of from about 1 to about 30 parts per 100 parts by total weight of polyol, though higher levels are highly desirable if they can be rendered compatible with the foam mixtures.
A supplemental blowing agent, water, may also be present. When present it is typically used in the amount from about 0.5-6 parts per 100 parts by weight of polyol. It is also possible to use conventional halogen-containing blowing agents and/or inert gases, e.g. CO2, as supplemental physical blowing agents.
Optionally, other ingredients may be present when preparing polyurethane foam. Among these are catalysts, surfactants, colorants, antioxidants, reinforcing agents, fillers, antistatic agents, and flame retardants. Suitable flame retardants include phosphorous containing substances such as tris (chloroalkyl) phosphate and trisalkylphosphates, for example triethylphosphate and nitrogen substances such as melamine.
One or more catalysts for the reaction of the active hydrogen-containing compound with the polyisocyanate are advantageously present. Suitable catalysts include tertiary amine compounds and organometallic compounds. Exemplary tertiary amine catalysts include triethylenediamine, pentamethyldiethylenetriamine, N,N-dimethylcyclohexylamine, N-ethylmorpholine, N-cocomorpholine, N-methylmorpholine, tetramethylethylenediamine, dimethylbenzylamine, 1-methyl-4-dimethylaminoethylpiperazine, 3-methyoxy-N-dimethylpropylamine, diethylethanolamine, N,N-dimethyl-Nxe2x80x2,Nxe2x80x2-dimethylisopropylpropylenediamine, N,N-diethyl-3-diethylaminopropylamine, and the like. Exemplary organometallic catalysts include organomercury, organolead, organoferric and organotin catalysts, with organotin catalyst being preferred among these. Suitable tin catalyst include stannous chloride, tin salts of carboxylic acids such as stannous octoate and stannous acetate, and dibutyltin di-2-ethylhexanoate, dibutyltin dilaurate and dibutyltin acetate, as well as the other organometallic compounds such as are disclosed in U.S. Pat. No. 2,846,408. A catalyst for the trimerization of polyisocyanate and formation of polyisocyanurate polymers, such as an alkali metal alkoxide, alkyl metal carboxylate or quaternary amine compound, may also optionally be employed herein. When employed, the quantity of catalyst used is sufficient to increase the rate of the polymerization reaction. Precise quantities must be determined experimentally, but generally will range from about 0.01 to about 3.0 parts by weight per 100 parts polyol depending on the type and activity of the catalyst.
This invention may also include the use of minor amounts of surfactant. Such surfactants, distinguished from the natural fatty oil based materials, are typically organosilicone surfactants. Such surfactants are employed in amounts sufficient to stabilize the foaming mixture against collapse and the formation of large, uneven cells. Typically from about 0.1-3.0 parts of surfactant per 100 parts by weight of polyol are sufficient for this purpose. Silicone surfactants for polyurethane foam manufacture typically are materials having siloxane backbones with polyether pendant groups, see for example, U.S. Pat. No. 3,842,112 and U.S. Pat. No. 3,933,695. Examples of such surfactants include Niax(copyright) L-6900 and Niax(copyright) L-5420 available from CK Witco Corp.
The compatibilizing agents of this invention are additives are alkoxylated triglyceride adducts (1) with a hydroxyl value of about 100 or less. The hydroxyl value is defined in units of mg KOH per gram of sample as measured according the ASTM standard method D-4274 or related methods. These compatibilizing agents may be optionally employed with one or more adduct species (2) from the following: a polyoxyalkylene oxide monol, a capped polyoxyalkylene oxide monol or polyol adduct or a fatty oil including triglyceride(s) and alkoxylated triglyceride(s).
The alkoxylated triglyceride adducts (1) used in the invention refers to all ethylene oxide, propylene oxide, butylene oxide or tetrahydrofuran based reaction products of triglycerides wherein the ethylene oxide content of the adduct is at least 40 weight percent, preferably greater than 50 weight percent, and most preferably greater than 60 weight percent, such that this adduct possesses a hydroxyl number of about 100 or less, preferably less than 90, and most preferably about 75 or less. The term triglyceride refers to fats, fatty oils, and derivatives that are nominally tricarboxylic esters of glycerol and may involve identical or different ester moieties on the same molecule. The average chain length for each of the three carboxylate moieties of the triglyceride is suitably at least 6 carbon atoms long, preferably at least 8 carbon atoms long. Such triglycerides include, but are not limited to, oils such as linseed, perilla, tung, safflower, soybean, castor, coconut, and cottonseed oils. As this invention relates to the alkoxylation of these triglycerides, this group is restricted to those fats, fatty oils, and derivatives, which can undergo alkoxylation reactions via standard chemistries known in the art. Accordingly, this invention relates to fats, fatty oils, and derivatives possess reactive amine, hydroxyl, or acid moieties. As is known in the art, the alkoxylation adducts produced in this manner are likely mixtures including fully etherified oil, partially etherified oil and unattached polyether. Such mixtures are suitably employed in the invention without isolation or purification of component species. A common fatty oil appropriate for practicing the invention is castor oil. A ring-opened, epoxidized derivative of an oil such as soybean oil would also fit this description. This latter material would be prepared from soybean oil in multiple reaction steps: typically an epoxidation reaction followed by a hydrolysis step followed by alkoxylation. Preferred alkoxylation adduct products are EO started.
The optional adduct species (2) includes one or more adducts from the following including mixtures: a polyoxyalkylene monol, which is derived from reactions of small molecules containing alcohol, amine, or acid functionality including mixtures with oxyethylene, oxypropylene, oxybutylene, or tetrahydrofuran mixtures thereof; a capped polyoxyalkylene monol, or polyol, adduct; or a fatty oil including triglycerides and alkoxylated triglycerides and capped versions of these, other than as defined for adduct species (1) above.
The capped species of this invention include adducts terminated with capping groups of acetoxy, methyl ether or ethyl ether. For this subgroup of structures the reactive hydroxyl groups of the alkoxylated triglyceride typically are substantially capped making them unreactive to isocyanate groups. These capping reactions typically are performed via reaction of hydroxyl groups with acetic anhydride, acetyl chloride, and methyl chloride, and the like.
The compatibilizing agent adduct (1), or the adduct mixture comprising adduct (1), is used in amounts from 0.1 to 10 parts per 100 parts of polyol by weight in the foam formulations of this invention, preferably from about 1.0 to 2.5 parts. The weight percent of the component (1) in the adduct mixtures including optional component (2) is 10 to 100%, preferably 25 to 100%, and most preferably 50 to 100%. The effectiveness of a particular amount of compatibilizing agent adduct or mixture will vary according to the composition of adducts (1) and adduct (2), if employed, the relative ratio, and the particularities of the remaining components of the foam system.
In making polyurethane foam, the polyol(s), polyisocyanate, compatibilizer and other components are contacted, thoroughly mixed, and permitted to expand and cure into a cellular polymer. The particular mixing apparatus is not critical, and various types of mixing head and spray apparatus are conventionally used. It is often convenient, but not necessary, to preblend certain of the raw materials prior to reacting the polyisocyanate with the active hydrogen-containing components. For example, it is often useful to blend the polyol(s), blowing agent, compatibilizer, surfactants, catalysts, and other components except for the polyisocyanate. Alternatively, all components can be introduced individually to the mixing zone where the polyisocyanate and polyol(s) are contacted. It is also possible to pre-react all or a portion of the polyol(s) with the polyisocyanate to from a prepolymer, although such is not preferred.
The polyurethane foam obtained in accordance with this invention is of value for the appliance and construction industry where its attractive compression strength, dimensional stability, and thermal insulation are highly desirable. The invention may also be used to provide polyurethane foam for semirigid applications such as for sealant foam applications.